Wait, only 7 gallons of old gas? How old?
Really, you could pretty easily mix 7 gal the old stuff, with 10 gal of 91 in a car that takes 87 and drive it off, especially at our altitude where we don't need the octane. Unless the gas is 10 years old and broken down to varnish, you'll be okay. Put in a family member or friends' car or something. Hell, split that 7 gallons across 3 cars and top them off w/ 91. It'll burn.
If you throw it out,
the terrorists win!?! 